Transmission Mode of Leprosy


Leprosy results from exposure of a person to a case of leprosy, It is important to note that prolonged contact with the person is necessary. Casual contact does not cause leprosy. This contact may be direct (e.g. skin to skin) or indirect (e.g. contact with soil, and fomites such as contaminated clothes and linen). Leprosy has a long incubation period, an average of about three to five years. The nose is a major portal of exit of organisms of a person affected by leprosy. Some cases of leprosy harbor millions of Mycobacterium leprae in their nasal mucosa which are discharged when they sneeze or blow the nose. The bacilli can also exit through ulcerated or broken skin of bacteriologically positive cases of leprosy.

It is generally agreed that people who harbor a large number of organisms, as their immune system cannot get rid of them, are the most important source of infection in the community. Among household contacts lepromatous cases, a varying proportion – roughly about 5 to 10% – is expected to show signs of leprosy within five years. This occurs despite treatment of the case, as the person usually harbors the organisms before exhibiting clinical signs and symptoms.

Leprosy occurs more commonly in males than in females in most regions of the world. Leprosy is not particularly a disease of children as was once believed.

Causative Factors Leprosy is caused by a bacterium, called Mycobacterium leprae which was first discovered Hansen of Norway in 1873. Thus the disease is also called Hansen’s disease.

Clinical Features It affects the peripheral nerves. It also affects the skin, muscles, eyes, bones, testes and internal organs.

Leprosy is characterized by one or more of the following signs

  • Hypopigmented patches.
  • Presence of thickened nerves.
  • Partial or total loss of cutaneous sensation in the affected area.
  • Presence of acid–fast bacilli in the skin or nasal smear.
  • In advanced stages of the disease, there is the presence of nodules or lumps on the skin of the face and ears.
  • Also, there is loss of fingers or toes, claw toes and various other deformities.

Inhalation A large number of bacilli are discharged by infectious patient while talking, coughing and sneezing. These bacilli enter health person through respiratory tract.

Contact Close, intimate and prolonged contact may be responsible for transmitting the disease.